The use of clinical devices in which pointed hollow needles or cannulas are employed in order to puncture the skin of a patient, and especially catheters utilizing such needles to effectuate venipunctures, is well known and widely practiced in the medical field for injecting drugs and fluids directly into the bloodstream of patients. Also, during surgery and other surgical procedures, it is often and frequently required that whole blood transfusions and parenteral fluids be administered to the patient undergoing such operations. The introduction of such fluids into the cardiovascular systems of patients has necessitated the forming of a venipuncture utilizing a hollow rigid needle having a proximal attachment site for fluid connection which is adapted to interconnect the needle with a source of intravenously administered fluids.
It is known in the medical art to introduce a thin tubular catheter of a low-friction biocompatible material into the vein of a patient and to permit the catheter tube to remain inserted over lengthier periods of time for purposes of, for example, periodically administering fluids, blood/plasma transfusions, medications in liquid form, collection of blood samples. By this procedure, the trauma, extravasation, and infiltration caused by repeated venipuncture have been largely avoided; it also overcomes the danger and discomfort caused due to leaving a needle inside the body. For the purpose of forming a venipuncture and inserting the catheter tube within the body cavity of a patient, such as a vascular cavaity or vein, the distal end of a flexible catheter tube is guided using a cannula or hollow sharp-tipped needle. Thereafter, the flexible catheter tube, which is slidably coaxially mounted on the outer circumference of the cannula or hollow needle, is advanced along the length of the needle into the vein subsequent to the needle having formed the venipuncture. Following venipuncture, the guide needle is withdrawn from the interior of the catheter tube, while permitting the catheter tube to remain inside the patient body at the site of the venipuncture. Thereafter, the used needle is suitably discarded according to the standard protocols prescribed for disposal.
The needle, which has been previously inserted in the body of the patient during venipuncture may have been exposed to infectious agents. For example, a patient infected with the Acquired Immune Deficiency Syndrome (AIDS) which is frequently or practically always ultimately fatal in nature, or other dangerous infectious conditions such as hepatitis, there is a constant danger or hazard that the clinical personnel or the para-medical staff may accidentally jab or stick themselves with the used needle after withdrawal from the body of the patient, with the possibility of infection or even death resulting therefrom.
Disposable medical devices having piercing elements administering a medicament or withdrawing a fluid require safe and convenient handling both prior to use and after use are known in the art.
For example, WO 2003/045480 relates to a safety needle assembly for injecting a fluid into a human body comprising a cylindrical housing with a bottom surface supporting a needle cannula and a shield telescopically movable relative to the housing. It discloses that a spring located within the housing is used to irreversibly immobilize the safety needle assembly.
U.S. Pat. No. 7,112,190 relates to a safety needle assembly with a needle hub and a needle cannula. It also has wings and describes that wings project transversely from the hub to facilitate manipulation and positioning of the needle assembly. It goes on to describe how a shield assembly is hingedly attached to the needle hub and can be rotated from a first position where the needle cannula is exposed to a second position where the needle cannula is shielded. A latch is also proposed to be disposed on the shield for securing locked engagement with the hub, the wings and/or the tubing extending from the hub. In addition, a spring is also suggested to propel the shield into the second position.
U.S. Pat. No. 7,163,526 discloses a needle assembly having an IV cannula, a non-patient cannula and a flash back chamber at the distal end of the housing. It discloses a shield connected hingably to a portion of the housing proximally of the entrance to the flashback chamber. Post use, the shield is rotated into a closed position to lock the used needle. Hingably connected shield is said to achieve clear visibility of the flashback chamber.
U.S. Pat. No. 7,128,726 discloses a safety shield assembly, which includes a clip with a plurality of cannula finger locks for preventing re-exposure of the used needle.
U.S. Pat. No. 7,041,092 discloses a shield system having a body, shield, spring and ring which provides an interlock of the shield in the retracted position.
Safe handling after use is more important to protect healthcare workers, paramedical staff and the medical personnel involved from needle stick injury. It is, therefore, desirable to shield the used needle cannula immediately after the needle cannula has been withdrawn from the patient. Such shields can prevent any accidental re-exposure of the used needle cannula and preferably, should prevent an intentional attempt to re-use the needle cannula. Such shields have been developed in different forms as described above. For example, some shields telescope in a distal to proximal direction over the needle cannula and frictionally engage the needle hub. However, such shields have risk of accidental needle stick injury if the shield in misaligned with the needle cannula. Other shields are telescoped over the needle hub and can be moved distally over the needle cannula to effect shielding, but such shields can interfere with the normal usage of some medical devices. Some devices employ very short needle cannulas, which are unsuitable if the shields are designed to lock near the distal end of needle cannula. Additionally, a shield designed to lock with a wider gauge needle cannula might be more likely to generate a spray upon engaging a much narrower needle cannula. Furthermore, it may be desirable to reduce the force required to effect shielding without reducing the audible and tactile indications of complete shielding.
Therefore, there exists a need of a safety device, which eliminates the chances of needle stick injuries both during insertion and after insertion and while disposing of the used needle.